Marine sediments monitoring studies for trace elements with the application of fast temperature programs and solid sampling high resolution continuum source atomic absorption spectrometry

• Analytical method based on solid sampling HR CS AAS for trace elements in marine sediments is presented.
• Full validation process for “fit-for-purpose” analytical procedure is described.
• Number of important validation parameters was systematically assessed.
• Modeling and single laboratory validation approaches for measurement uncertainty are presented.
• Demonstration of traceability of measurement results is also provided.

Analytical procedure for the determination of As, Cd, Cu, Ni, Co and Cr in marine sediment samples using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR CS AAS) and direct solid sample analysis has been developed. The application of fast programs in combination with direct solid sampling allows to eliminate the drying and pretreatment steps, however makes impossible the use of liquid standards for calibration. Iridium treated platforms were applied throughout the present study. Calibration technique based on the use of solid certified reference materials (marine sediments) similar to the nature of the analyzed sample and statistics of regression analysis were applied to the real sediment samples. The instrumental parameters were optimized in order to obtain reproducible and interference free analytical signals. The ISO-17025 requirements and Eurachem guidelines were followed in the validation of the proposed analytical procedure. Accordingly, blanks, selectivity, calibration, linearity, working range, trueness, repeatability reproducibility, limits of detection and quantification and expanded uncertainty (k = 2) for all investigated elements were assessed. Two different approaches for the estimation of measurement uncertainty were applied and obtained results compared. The major contributors to the combined uncertainty of the analyte mass fraction were found to be the homogeneity of the samples and the microbalance precision. The influence of sample particle sizes on the total combined uncertainty was also evaluated.Traceability to SI system of units of the obtained by the proposed analytical procedure results was demonstrated.Additionally, validation of the methodology developed was effectuated by the comparison of the obtained results with independent method e.g. ICP-MS with external calibration. The use of solid sampling HR CS AAS for the determination of trace elements in marine sediment matrix gives significant advantages, such as straightforward calibration, a high sample throughput, sufficient precision, suitable limits of detection, appropriate for monitoring studies concentration range and reduced risk of analyte loss and contamination. This approach allows comparatively simple and reliable evaluation of uncertainty of the results and the basic validation parameters and in a natural way provides traceability of the obtained results. A comparison between the proposed fast programs with solid standard calibration and the conventional ones with liquid standard calibration demonstrates advantages of the new methodology. It provides faster, accurate and unbiased results typically with significantly lower uncertainties.The potential of the HR CS AAS technique is demonstrated by direct analysis of marine sediments form the Caribbean region and various sediment CRMs within the frame of monitoring program for this region.